Facebook and Twitter face sanctions unless they comply with European consumer rules by the end of the year, the EU said as its regulators continue to their crackdown on US social media giants over privacy concerns.

Online platforms have come under fire in Europe because of their dominance and anti-competitive business practices, resulting in hefty fines handed down to some companies.

Seven months after being told to bring their user terms in line with EU regulations, both Facebook and Twitter have yet to fully address all the issues, the European Commission said on Thursday.

In contrast, Airbnb made the necessary changes after being told to do so three months ago, European Justice Commissioner Vera Jourova said, confirming a Reuters story on Wednesday. “If we don’t see progress, the sanctions will come,” she told a news conference. "This is quite clear. We cannot negotiate for ever, we need to see the results.”

Twitter should also make the necessary changes by year-end, a Commission spokesman said. Any sanctions would be imposed by national consumer bodies. The Commission has previously said it was worried about the companies’ liability and how users are informed about content removal or contract terminations.

Facebook said it had already made a number of changes and would continue to cooperate with the authorities. “We updated Facebook’s terms of service in May and included the vast majority of changes the Consumer Protection Cooperation Network and the European Commission had proposed at that point,” the company said in a statement.

“Our terms are now much clearer on what is and what isn’t allowed on Facebook and on the options people have.”

Changes to Airbnb’s user terms include showing the total price of bookings and extra fees, whether the offer is made by a private host or by a professional and that consumers have the right to take legal action.